907 research outputs found
End-to-end encryption of modern messaging
No full textMet moderne hackingtools is het niet langer voldoende om cryptografische sleutels te lang in de buurt te houden, met oude cryptografische algoritmen, als een sleutel wordt gelekt, wordt de meeste communicatie gecompromitteerd, nieuwe algoritmen bestrijden dit door sleutels vaak te roteren. Voor client-servercommunicatie is dit probleem niet moeilijk, aangezien zowel client als server altijd online zijn en nieuwe sleutels snel kunnen worden berekend. Met moderne end-to-end versleutelde (E2EE) messaging, zoals bij Signal en Whatsapp, zijn de deelnemende partijen mogelijk niet tegelijkertijd online.
Om dit op te lossen, roteren moderne E2E hybride cryptografische algoritmen automatisch sleutels op een asynchrone manier.
In dit proefschrift worden verschillende van deze algoritmen uitgelegd, waaronder het aandrijfalgoritme achter Signal en Whatsapp: het Double Ratchet Algorithm.
Om deze algoritmen beter te begrijpen en waarom ze nodig zijn, wordt informatie gegeven over de doelen die ze proberen te bereiken en welke meer basale algoritmen worden gebruikt als bouwstenen om de moderne hybride cryptografische algoritmen te construeren.
Dit proefschrift biedt ook een interactieve visualisatietool die laat zien hoe de cryptografische sleutels worden gegenereerd in het Double-Ratchet-algoritme
Progressive Network Streaming of Textured Meshes in the Binary glTF 2.0 Format
No full textThe glTF 2.0 graphics format allows for the API-neutral representation of 3D scenes consisting of one or multiple textured meshes. It is currently adopted as one of two file formats for 3D asset interop-erability by the Metaverse Standards Forum. glTF 2.0 has however not been designed to be streamable over the network; instead, glTF 2.0 files typically first need to be downloaded fully before their contents can be rendered locally. This can lead to high start-up delays which in turn can lead to user frustration. This paper therefore contributes a methodology and associated Web-based client, implemented in JavaScript on top of the three.js rendering engine, that allows to stream glTF 2.0 files from a content server to the consuming client up to the level of individual glTF bufferviews. This in turn facilitates the progressive client-side rendering of 3D scenes, meaning that scene rendering can already commence while the glTF file is still being downloaded. The proposed methodology is conceptually compliant with the HTTP Adaptive Streaming (HAS) paradigm that dominates the contemporary market of over-the-top video streaming. Experimental results show that our methodology is most beneficial when network throughput is limited (e.g., 20Mbps). In all, our work represents an important step towards making 3D content faster accessible to consuming (Web) clients, akin to the way platforms like YouTube have brought universal accessibility for video content
Digging through the dirt: a general method for abstract discrete state estimation with limited prior knowledge
No full textAutonomous robots are often successfully deployed in controlled environments. Operation in uncontrolled situations remains challenging; it is hypothesized that the detection of abstract discrete states (ADS) can improve operation in these circumstances. ADS are high-level system states that are not directly detectable and influence system dynamics. An example of a typical ADS problem that is used in this thesis is that of a wheeled robot driving through puddles of mud that, when entered, alters the velocity of the robot. When the robot is in such a puddle, it is in an ADS 'mud', and when it is not, it is in an ADS 'free'. ADS can be indirectly inferred through the analysis of lower-level data such as the velocity of the robot. The goal of this thesis is to design a general abstract discrete state estimator (ADSE) operating with limited prior knowledge. An ADSE is a hierarchical system for detecting changes in ADS. The ADSE should be general; applicable to multiple ADSE problems. The ADSE should further operate under limited prior knowledge: only assuming that the amount of ADS and the ADS that describes the regular operation are known. The basis for the ADSE designed in this thesis is a Gaussian hidden Markov model (GHMM), a hidden Markov model enhanced with Gaussian emissions. Randomly generated experiments are done on a simple but general ADSE problem. Two unsupervised learning methods derived from Expectation Maximization are evaluated, namely Baum-Welch (BW) and forward extraction (FWE). FWE is introduced in this thesis and is a simpler implementation of Viterbi extraction, leveraging assumptions of ADSE to in theory gain computational efficiency. We found that both BW and FWE exhibit superior performance compared to a likelihood-based baseline estimator when the maximum score of the learning curve is considered. When the final score is considered, in some cases, FWE displays a deteriorating learning curve, resulting in worse final scores compared to the baseline. Furthermore, it was found that the lower the overlap coefficient (therefore the less similar the ADS), the higher the maximum reached score. It was further shown that BW exhibits better convergence than FWE to the true model parameters. Besides this, FWE obtained comparable or in some cases even superior scores compared to BW. In general, from the results, the diversity of the experiments conducted, and the assumptions made we can conclude that the GHMM can be a general method for an ADSE with limited prior knowledge. To quantify the suitability of the GHMM for ADSE, further research should include the evaluation of different ADSE methods on the same problem. There exists a tradeoff between the lower computational cost FWE and the more stable but more computationally intensive BW learning. Therefore, future research can include a combination of these methods. Other extensions include extending the GHMM to a Gaussian mixture hidden Markov model to allow for the modeling of more complex distributions, or the application to multiple states or a changing environment.https://github.com/Wouter-deBoer/adseMechanical Engineering | Vehicle Engineering | Cognitive Robotic
embalming and reperfusion of porcine kidneys
No full text<p>These are the data of the following article:</p>
<p>Understanding Thiel embalming in pig kidneys to develop a new circulation model</p>
<p>First author: Wouter Willaert</p
Nederland op een kantelpunt: Interview met Wouter Veldhuis over het Stedelijk Netwerk Nederland en het sociaal netwerk van woonwijken
No full textDe stedenbouwkundige en architect Wouter Veldhuis en landschapsarchitect Jannemarie de Jonge zijn per 1 december 2020 Rijksadviseur voor de fysieke leefomgeving. Later in september 2021 komt daar de architect Francesco Veenstra bij als Rijksbouwmeester en dan is het nieuwe trio College van Rijksadviseurs weer compleet. De uitdagingen voor het college zijn groot. De ruimteclaims die er liggen in stad en land, de hooggestemde ambities om klimaatneutraal en circulair te zijn in 2050, de roep om een minister voor de fysieke leefomgeving en of wonen en weer een echt ministerie met budget. Het enorme probleem op de woningmarkt en de druk om één miljoen woningen ergens bij te bouwen. Op 24 april sprak het team van 1M Homes initiative van de TU Delft met de nieuw benoemde rijksadviseur voor de fysieke leefomgeving Wouter Veldhuis over de aanstaande veranderingen
Does Indonesia have a"low-pay"civil service?
No full textGovernment officials and polcy analysts maintain that Indonesia's civil servants are poorly paid and have been for decades. This conclusion is supported by anecdotal evidence and casual empiricism. The authors systematically analyze the realtionship between government and private compensation levels using data from two large household surveys carried out by Indonesia's Central Bureau of Statistics: the 1998 Sakernas and 1999 Susenas. The results suggest that government workers with a high school education or less, representing three-quarters of the civil service, earn a pay premium over their private sector counterparts. Civil servants with more than a high school education earn less than they would in the private sector but, on average, the premium is far smaller than commonly is alleged and is in keeping with public/private differentials in other countries. These results prove robust to varying econometric specifications and cast doubt on low pay as an explanation for government corruption.Decentralization,Public Health Promotion,Health Monitoring&Evaluation,National Governance,Knowledge Economy,Health Monitoring&Evaluation,NationalGovernance,Knowledge Economy,Education for the Knowledge Economy,Parliamentary Government
Optimization of the capacity of a rose sorting system using discrete event simulation
No full textIn Rose cultivation companies in the Netherlands, there is a demand for a higher sorting capacity on the existing sorting systems. The objective for this research is to advice which part of the sorting system needs to be adjusted to gain a higher sorting capacity. For the current sorting systems, five bottlenecks are defined, the bottlenecks limit the sorting capacity. To be able to forecast the effect of machine adjustments, a discrete event simulation model has been constructed, using Simulink and Matlab. This simulation model is verified, matched and validated using data of on an existing rose sorting system. Results of a single day validation showed that the time to process the roses can be simulated with a 97% accuracy. Subsequently, five different simulations are executed. In each simulation, one of the five bottlenecks is removed or reduced. With the results of these simulations the capacity limitation due to each bottleneck is quantified. However entirely removing a bottleneck is not feasible in reality for all bottlenecks. A last situation is simulated where all feasible bottleneck reductions are combined. This showed that the time to sort all roses is reduced by 35%.Marine Technology | Transport Engineering and Logistic
Single-component organic solar cells-Perspective on the importance of chemical precision in conjugated block copolymers
No full textThe author(s) declare financial support was received for the research, authorship, and/or publication of this article. The authors acknowledge financial support from Hasselt University, the Research Foundation-Flanders (FWO Vlaanderen; projects W000620N, I006320N, and 1S99620N), and the European Research Council (ERC; grant agreement 864625)
From exemplar to copy: the scribal appropriation of a Hadewijch manuscript computationally explored
No full textThis study is devoted to two of the oldest known manuscripts in which the
oeuvre of the medieval mystical author Hadewijch has been preserved: Brussels,
KBR, 2879-2880 (ms. A) and Brussels, KBR, 2877-2878 (ms. B). On the basis of
codicological and contextual arguments, it is assumed that the scribe who
produced B used A as an exemplar. While the similarities in both layout and
content between the two manuscripts are striking, the present article seeks to
identify the differences. After all, regardless of the intention to produce a
copy that closely follows the exemplar, subtle linguistic variation is
apparent. Divergences relate to spelling conventions, but also to the way in
which words are abbreviated (and the extent to which abbreviations occur). The
present study investigates the spelling profiles of the scribes who produced
mss. A and B in a computational way. In the first part of this study, we will
present both manuscripts in more detail, after which we will consider prior
research carried out on scribal profiling. The current study both builds and
expands on Kestemont (2015). Next, we outline the methodology used to analyse
and measure the degree of scribal appropriation that took place when ms. B was
copied off the exemplar ms. A. After this, we will discuss the results
obtained, focusing on the scribal variation that can be found both at the level
of individual words and n-grams. To this end, we use machine learning to
identify the most distinctive features that separate manuscript A from B.
Finally, we look at possible diachronic trends in the appropriation by B's
scribe of his exemplar. We argue that scribal takeovers in the exemplar impacts
the practice of the copying scribe, while transitions to a different content
matter cause little to no effect
The Power of Ideas: Esotericism, Historicism, and the Limits of Discourse
No full textThis article is a response to the reviews by Giovanni Filoramo, Olav Hammer, Bernd-Christian Otto, Marco Pasi, and Michael Stausberg of Wouter J. Hanegraaff's book Esotericism and the Academy: Rejected Knowledge in Western Culture. The author attempts to clarify his view of the relation between history and theory, and between intellectual history and discourse theory in particular; he provides a summary of his motivations for writing the book and of its main argument; he concludes by addressing a number of theoretical issues raised by the respondents
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